Pathology-White Cell Disorder Pathology Flashcards
What is the marker for the hematopoietic stem cell in the bone marrow?
CD34
How does differentiation of the hematopoietic stem cell proceed down the lymphoid route?
The lymphoid stem cell (blast) can differentiate into a B lymphoblast or a T lymphoblast. They can then become naive B cells and T cells respectively. The naive B cell then becomes a plasma cell. The naive T cells differentiate into CD8+ or CD4+ T cells.

How does differentiation of the hematopoietic stem cell proceed down the myeloid route?
The myeloid stem cell (blast) can differentiate into an erythroblast and become an RBC, a myeloblast and become a neutrophil, basophil or eosinophil, a monoblast and become a monocyte and a megakaryoblast to become a megakaryocyte.

Normal WBC count
5-10K. < 5K = leukopenia. >10K = leukocytosis.
Common causes of neutropenia
Drug toxicity (chemotherapy blocks hematopoiesis) and severe infection (most of the neutrophils have left the blood and are in the tissue)
How do you treat a patient who is on chemotherapy that has neutropenia?
GM-CSF or G-CSF. Both of these will help to boost the neutrophil count.
Common causes of lymphopenia
Immunodeficiency (DiGeorge failure to develop 3rd and 4th pharyngeal pouch = failure to develop thymus = failure to develop T cells), high cortisol state (induces lymphocytic apoptosis), autoimmune destruction (Lupus produces antibodies against WBCs) and whole body radiation (lymphocytes are most sensitive cells in the body to radiation).
Common causes of neutrophilic leukocytosis
Bacterial infection and tissue necrosis from acute inflammatory process. High cortisol state (marginated pool of neutrophils are released from cortisol breaking the adhesion molecule to the pulmonary endothelium).
Why don’t band cells work as well as grown up neutrophils during acute inflammation?
When they are released early from the bone marrow they have decreased CD16 (Fc receptor). This results in decreased recognition of immunoglobulins that have opsonized invading pathogens.
Common causes of monocytosis
Chronic inflammatory states and malignancy
Common causes of eosinophilia
Allergic reactions, parasitic infections and Hodgkin lymphoma (due to increased IL-5 production)
Common cause of basophilia
CML
Common causes of lymphocytic leukocytosis
Viral infections (CD8+ T-cells are main fighters of virus and are released into the blood in an infection) and Bordetella pertussis (bacteria produces lymphocytosis promoting factor, this prevents lymphocytes from exiting the blood and going to the lymph nodes)
A 17 year old boy comes to see you complaining of a sore throat, fever and fatigue. Physical exam reveals posterior cervical lymphadenopathy and splenomegaly. Peripheral blood smear is shown below. What is causing his condition?

Note the atypical lymphocyte (CD8+ T-cell nucleus much larger than RBCs with abundant cytoplasm, note that it looks like a monocyte). This patient has infectious mononucleosis. Salivary transmission of EBV is the most common cause and CMV is the less common cause. EBV targets the oropharynx, liver and B cells during an infection.
A 17 year old boy comes to see you complaining of a sore throat, fever and fatigue. Physical exam reveals posterior cervical lymphadenopathy and splenomegaly. Labs reveal a high white count and atypical lymphocytes. Which area of the lymph node is causing lymphadenopathy?
He has infectious mononucleosis, most likely from an EBV infection. The immune response to this is release of CD8+ T-cells. In the lymph node, B-cells are in the cortex and T-cells are in the paracortex, so you will have enlargement of the lymph node’s paracortex.
A 17 year old boy comes to see you complaining of a sore throat, fever and fatigue. Physical exam reveals posterior cervical lymphadenopathy and splenomegaly. Labs reveal a high white count and atypical lymphocytes. What area of the spleen is causing splenomegaly?
The red pulp of the spleen contains blood. The white pulp contains lymphoid tissue, which contains B cell and T cell areas. The periarterial lymphatic sheath (PALS) in the white pulp is where the T-cells are and will be expanded when patients have an EBV infection, causing splenomegaly.

A 17 year old boy comes to see you complaining of a sore throat, fever and fatigue. Physical exam reveals posterior cervical lymphadenopathy and splenomegaly. Labs show a high white count and atypical lymphocytes. How are you going to test for disease in this patient?
Monospot test: detects IgM heterophile antibodies (binds sheep/hoarse RBCs). The spot will turn positive within 1 week if he has EBV. Since this is a screening test, diagnosis is confirmed by EBV viral capsid antigen presence. If the monospot test is negative, CMV is the cause.
A 17 year old boy comes to see you complaining of a sore throat, fever and fatigue. Physical exam reveals posterior cervical lymphadenopathy and splenomegaly. Labs show a high white count and atypical lymphocytes. What complications is he at risk for?
Splenic rupture (should avoid contact sports for 1 year), rash if exposed to penicillin, EBV remains dormant in B cells (increases risk for lymphoma and recurrent mononucleosis).

What is the definition of an acute leukemia?
>20% blasts in the bone marrow
What symptoms often present in patients with acute leukemia?
The blasts crowd out the normal hematopoietic cells. This causes sudden-onset anemia (hypoxia), thrombocytopenia (bleeding) and neutropenia (infection).
What would you expect to see on CBC of a patient with acute leukemia?
High WBC. Large, immature cells with punched out nucleoli on peripheral blood smear.

A 7 year old boy presents with sudden onset dyspnea, bleeding from the gums and recurrent infections in the past month. CBC shows high WBC count and peripheral blood smear is shown below. How do you proceed from here to narrow your diagnosis?

The patient is presenting with symptoms of acute leukemia, confirmed by blast cells on peripheral blood smear. Now you need to determine if the cell is a myeloblast or a lymphoblast. Myeloblasts will stain positive for myeloperoxidase (or seen visually as Auer rods) and indicates acute myelogenous leukemia. The DNA polymerase, tDt, will be positive in the nucleus of lymphoblasts and indicates acute lymphoblastic leukemia.
A 6 year old Down-Syndrome boy presents with sudden onset dyspnea, bleeding from the gums and recurrent infections in the past month. CBC shows high WBC count and peripheral blood smear shows immature blasts. Labs reveal that the blasts are tDt positive. What is your diagnosis?
There is a high association of ALL with Down Syndrome in kids older than 5 years old. Note that AML:acute megakaryoblastic leukemia more commonly presents before the age of 5.
A 7 year old boy presents with sudden onset dyspnea, bleeding from the gums and recurrent infections in the past month. CBC shows high WBC count and marrow aspirate shows immature blasts that are tDt positive. What markers to you use to further narrow your diagnosis?
B cell acute lymphoblastic leukemia (the most common type of ALL) classically expresses CD10, 19 and 20. T cell acute lymphoblastic lymphoma classically expresses CD2-8 and does not express CD10. Note that T-cell is called lymphoma because cells are not floating around in the blood.




























